Abstract: A protective device for use on a wheeled vehicle such as a tractor pulled trailer equipped with an air brake is provided. The air brake includes a housing generally disposed lengthwise of the trailer and comprises a transversely disposed diaphragm in a medial portion thereof with air pressure communicating with the front side of the diaphragm and further comprises a heavy coiled spring positioned in opposition to the air pressure on the rear side of the diaphragm. A protective device in the form of a perforated plate is mounted adjacent to and rearwardly of the housing so as to be in the path of the coiled spring in the event of rupturing of the housing, as from corrosion, and releasement of the spring therefrom, to prevent the spring from being projected rearwardly away from the housing.